Why do you tell it should only work well if len(A) is small? batched_dot should work well for a big len(A).
Fred On Wed, Feb 15, 2017 at 10:50 AM Adam Becker <[email protected]> wrote: > Besides that, use subtensor and batched_dot can further vectorize things. > > > A = T.batched_dot(A[::2], A[1::2]) # if len(A)|1 == 0 > > > > This should work well as long as len(A) contains only small prime factors > > On Wednesday, February 15, 2017 at 9:02:34 PM UTC+8, Kiuhnm Mnhuik wrote: > > I don't know how Theano works internally, so this might not work. > First compute A[0] = A[0] x A[1]; A[1] = A[2] x A[3]; A[2] = A[4] x A[5]; > etc... > Then repeat until you have just one matrix. If N is a power of 2 it's > easier... > > On Wednesday, February 15, 2017 at 12:33:40 PM UTC+1, [email protected] > wrote: > > Hi, > > *Goal * > In the context of a learning algorithm, I want to calculate the > product: > > B = A[K-1] x A[K-1] x .... A[0], > > where each A[k] is a (sparse, if it helps to know) matrix of size N*N and > "x" denotes the theano.dot() product . > > *Question * > * How can I do that for fairly large matrices, say each A[k] is *100x100* > ? * > > *Things I've tried (t is theano and tt is theano.tensor):* > > - *For loop* > > B = tt.eye(n=self.N, m=N)for k in range(0, K-1): > B = t.dot(A[k], B) > > *Pro*: simple, works fine for N = 10 > *Con*: If N >> (say N = 100), I get this error: > File "/usr/local/lib/python2.7/dist-packages/theano/gof/graph.py", line > 392, in __init__self.auto_name = 'auto_' + str(next(self.__count__)) > RuntimeError: maximum recursion depth exceeded while getting the str of an > object > > > - *Theano scan or reduce* > > results, _ = t.scan(fn=lambda k, tmp: tt.dot(A[k], tmp), > outputs_info=tt.eye(n=N, m=N), > sequences=[tt.arange(K, dtype='int64')]) > B = results[-1] > > > > *Pro*: works even for large matrices > *Con*: Epoch become incredibly slow (200,000 seconds instead of 500~1,000) > > > > Any help or advice would be much appreciated. > > Thanks > Oussama > > > -- > > --- > You received this message because you are subscribed to the Google Groups > "theano-users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > For more options, visit https://groups.google.com/d/optout. > -- --- You received this message because you are subscribed to the Google Groups "theano-users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
